In a manufacturing process of a semiconductor device, a probe test is performed to evaluate an electrical characteristic of the semiconductor device. The probe test is performed by making probe needles contact with electrodes of semiconductor devices formed on a semiconductor substrate, inputting electric signals to each of the semiconductor devices, and observing electric signals outputted in response to the input signals, thereby evaluating electrical characteristics of the semiconductor devices.
A probe apparatus used in the probe test includes: a stage that holds a substrate on which a semiconductor device to be tested is formed, the stage being rotatable and movable in horizontal and vertical directions; and an alignment device for making probe needles exactly contact with electrodes of the semiconductor device formed on the substrate. As the alignment device, there is suggested one having a first camera for detecting the positions of the probe needles and a second camera for detecting the position of the semiconductor device formed on a surface of the substrate (see, e.g., Japanese Patent Application Publication Nos. H8-335612 and H7-297241). In the probe apparatus, in order to perform a position alignment between the probe needles and the electrodes, the following process is performed: a process of obtaining as coordinates the positions of the probe needles by using the first camera; a process of aligning the positions of the first and second cameras by a movable mechanical target; and a process of obtaining as coordinates the positions of the electrodes on the substrate by using the second camera.
As in the above references, in a method of performing a position alignment of a pair of cameras by using the mechanical target, there is required an operation of moving the target back and forth toward the vicinity of the focuses of the first and second cameras. For this reason, there is concerned that a failure may occur due to a contact of the mechanical target with another member of the probe apparatus by malfunction and particles may be generated from a driving mechanism of the mechanical target. Further, since the driving mechanism of the mechanical target is complicated, there arise problems that the number of the components is large, miniaturization is difficult, the cost is high, and a regular maintenance is required. Furthermore, in the mechanical target, since a glass plate having a target mark formed thereon is used, the amount of the refraction is changed depending on the thickness of the glass plate. As a result, from one of the cameras, an error occurs in a thickness direction of the glass plate. Therefore, there arises a problem of degrading an accuracy of the position alignment.
Instead of the mechanical target, a method is known in which the positions of a pair of cameras are aligned by using an optical unit (see, e.g., Japanese Patent Application Publication Nos. 2003-303865 and 2010-219110). In Japanese Patent Application Publication No. 2003-303865, there is suggested a probe apparatus that performs a position alignment by allowing a spot light to proceed along an optical axis of one of the cameras and to be recognized by the other camera. In Japanese Patent Application Publication No. 2010-219110, there is suggested a probe apparatus including a projection optical system that projects a two-dimensional pattern from one of the cameras toward the other of the cameras.
In Japanese Patent Application Publication Nos. 2003-303865 and 2010-219110 which perform the position alignment of a pair of cameras by using the optical unit, when performing the position alignment, the both cameras cannot simultaneously recognize the spot light or the two-dimensional pattern which serves as a substitute of the target mark. For this reason, in the conventional technologies, the position alignment needs to be performed in plural steps. As a result, more effort and time is required for the position alignment, and thus a throughput is lowered in the entire probe test.
Further, in the position alignment methods of Japanese Patent Application Publication Nos. 2003-303865 and 2010-219110, since the spot light or the two-dimensional pattern cannot be recognized by the both camera at the same time, there is required an operation for recognizing the spot light or the two-dimensional pattern by inserting an opaque object onto an optical axis of any one of the cameras. Accordingly, in the position alignment methods of Japanese Patent Application Publication Nos. 2003-303865 and 2010-219110, a movable member is used, so that most of the above problems occurring in the methods of employing the conventional mechanical target remains not solved.
For example, in the probe apparatus disclosed in Japanese Patent Application Publication No. 2003-303865, in a camera placed in an irradiating side of the spot light, the position alignment between an optical axis of the camera and the spot light becomes impossible until the spot light is imaged on a surface of an object that blocks an optical axis of the spot light. In the probe apparatus disclosed in Japanese Patent Application Publication No. 2010-219110, since the two-dimensional pattern cannot be recognized directly by a camera placed near the projection optical system, it is required to previously pick up a real image of the two-dimensional pattern by inserting an object such as an opaque plate or the like so as to block light from the camera, and store its coordinates.